Dubbo源码学习--Redis注册中心（三）

基于 Redis 1​ 实现的注册中心 2。

使用 Redis 的 Key/Map 结构存储数据结构：

• 主 Key 为服务名和类型
• Map 中的 Key 为 URL 地址
• Map 中的 Value 为过期时间，用于判断脏数据，脏数据由监控中心删除3

使用 Redis 的 Publish/Subscribe 事件通知数据变更：

• 通过事件的值区分事件类型：

​​register​​

• ,

​​unregister​​

• ,

​​subscribe​​

• ,

​​unsubscribe​​

• 普通消费者直接订阅指定服务提供者的 Key，只会收到指定服务的

​​register​​

• ,

​​unregister​​

• 监控中心通过

​​psubscribe​​

• 功能订阅

​​/dubbo/*​​

• ，会收到所有服务的所有变更事件

调用过程：

服务提供方启动时，向

​​Key:/dubbo/com.foo.BarService/providers​​

并向

​​Channel:/dubbo/com.foo.BarService/providers​​

发送

​​register​​

服务消费方启动时，从

​​Channel:/dubbo/com.foo.BarService/providers​​

订阅

​​register​​

和

​​unregister​​

并向

​​Key:/dubbo/com.foo.BarService/providers​​

服务消费方收到

​​register​​

和

​​unregister​​

事件后，从

​​Key:/dubbo/com.foo.BarService/providers​​

服务监控中心启动时，从

​​Channel:/dubbo/*​​

订阅

​​register​​

和

​​unregister​​

，以及

​​subscribe​​

和

​​unsubsribe​​

事件

服务监控中心收到

​​register​​

和

​​unregister​​

事件后，从

​​Key:/dubbo/com.foo.BarService/providers​​

下获取提供者地址列表

服务监控中心收到

​​subscribe​​

和

​​unsubsribe​​

事件后，从

​​Key:/dubbo/com.foo.BarService/consumers​​

配置

<dubbo:registry address="redis://10.20.153.10:6379"

或

<dubbo:registry address="redis://10.20.153.10:6379?backup=10.20.153.11:6379,10.20.153.12:6379"

或

<dubbo:registry protocol="redis" address="10.20.153.10:6379"

或

<dubbo:registry protocol="redis" address="10.20.153.10:6379,10.20.153.11:6379,10.20.153.12:6379"

选项

• 可通过

​​<dubbo:registry group="dubbo" />​​

• 设置 redis 中 key 的前缀，缺省为

​​dubbo​​

• 。
• 可通过

​​<dubbo:registry cluster="replicate" />​​

• 设置 redis 集群策略，缺省为

​​failover​​

• ：

​​failover​​

• : 只写入和读取任意一台，失败时重试另一台，需要服务器端自行配置数据同步

​​replicate​​

• : 在客户端同时写入所有服务器，只读取单台，服务器端不需要同步，注册中心集群增大，性能压力也会更大

可靠性声明

阿里内部并没有采用 Redis 做为注册中心，而是使用自己实现的基于数据库的注册中心，即：Redis 注册中心并没有在阿里内部长时间运行的可靠性保障，此 Redis 桥接实现只为开源版本提供，其可靠性依赖于 Redis 本身的可靠性。

Redis注册中心实现了RedisRegistryFactory工厂，用来生成Registry的实现类RedisRegistry。

public class RedisRegistryFactory extends AbstractRegistryFactory {

@Override
protected Registry createRegistry(URL url) {
return new RedisRegistry(url);
}
}

RedisRegistry中主要实现了如下接口：

（1）doRegister(URL url);//向注册中心注册服务

（2）doUnregister(URL url);//取消服务注册

（3）doSubscribe(URL url, NotifyListener listener);//向注册中心监听服务

（4）doUnsubscribe(URL url, NotifyListener listener);//取消监听注册中心服务

public class RedisRegistry extends FailbackRegistry {

private static final Logger logger = LoggerFactory.getLogger(RedisRegistry.class);

private static final int DEFAULT_REDIS_PORT = 6379;

private final static String DEFAULT_ROOT = "dubbo";

private final ScheduledExecutorService expireExecutor = Executors.newScheduledThreadPool(1, new NamedThreadFactory("DubboRegistryExpireTimer", true));

private final ScheduledFuture<?> expireFuture;

private final String root;

private final Map<String, JedisPool> jedisPools = new ConcurrentHashMap<String, JedisPool>();

private final ConcurrentMap<String, Notifier> notifiers = new ConcurrentHashMap<String, Notifier>();

private final int reconnectPeriod;

private final int expirePeriod;

private volatile boolean admin = false;

private boolean replicate;

//构造函数中主要完成了redis连接相关的操作
public RedisRegistry(URL url) {
super(url);
if (url.isAnyHost()) {
throw new IllegalStateException("registry address == null");
}
GenericObjectPoolConfig config = new GenericObjectPoolConfig();
config.setTestOnBorrow(url.getParameter("test.on.borrow", true));
config.setTestOnReturn(url.getParameter("test.on.return", false));
config.setTestWhileIdle(url.getParameter("test.while.idle", false));
if (url.getParameter("max.idle", 0) > 0)
config.setMaxIdle(url.getParameter("max.idle", 0));
if (url.getParameter("min.idle", 0) > 0)
config.setMinIdle(url.getParameter("min.idle", 0));
if (url.getParameter("max.active", 0) > 0)
config.setMaxTotal(url.getParameter("max.active", 0));
if (url.getParameter("max.total", 0) > 0)
config.setMaxTotal(url.getParameter("max.total", 0));
if (url.getParameter("max.wait", url.getParameter("timeout", 0)) > 0)
config.setMaxWaitMillis(url.getParameter("max.wait", url.getParameter("timeout", 0)));
if (url.getParameter("num.tests.per.eviction.run", 0) > 0)
config.setNumTestsPerEvictionRun(url.getParameter("num.tests.per.eviction.run", 0));
if (url.getParameter("time.between.eviction.runs.millis", 0) > 0)
config.setTimeBetweenEvictionRunsMillis(url.getParameter("time.between.eviction.runs.millis", 0));
if (url.getParameter("min.evictable.idle.time.millis", 0) > 0)
config.setMinEvictableIdleTimeMillis(url.getParameter("min.evictable.idle.time.millis", 0));

String cluster = url.getParameter("cluster", "failover");
if (!"failover".equals(cluster) && !"replicate".equals(cluster)) {
throw new IllegalArgumentException("Unsupported redis cluster: " + cluster + ". The redis cluster only supported failover or replicate.");
}
replicate = "replicate".equals(cluster);

List<String> addresses = new ArrayList<String>();
addresses.add(url.getAddress());
String[] backups = url.getParameter(Constants.BACKUP_KEY, new String[0]);
if (backups != null && backups.length > 0) {
addresses.addAll(Arrays.asList(backups));
}

String password = url.getPassword();
for (String address : addresses) {
int i = address.indexOf(':');
String host;
int port;
if (i > 0) {
host = address.substring(0, i);
port = Integer.parseInt(address.substring(i + 1));
} else {
host = address;
port = DEFAULT_REDIS_PORT;
}
if (StringUtils.isEmpty(password)) {
this.jedisPools.put(address, new JedisPool(config, host, port,
url.getParameter(Constants.TIMEOUT_KEY, Constants.DEFAULT_TIMEOUT)));
} else {
this.jedisPools.put(address, new JedisPool(config, host, port,
url.getParameter(Constants.TIMEOUT_KEY, Constants.DEFAULT_TIMEOUT), password));
}
}

this.reconnectPeriod = url.getParameter(Constants.REGISTRY_RECONNECT_PERIOD_KEY, Constants.DEFAULT_REGISTRY_RECONNECT_PERIOD);
String group = url.getParameter(Constants.GROUP_KEY, DEFAULT_ROOT);
if (!group.startsWith(Constants.PATH_SEPARATOR)) {
group = Constants.PATH_SEPARATOR + group;
}
if (!group.endsWith(Constants.PATH_SEPARATOR)) {
group = group + Constants.PATH_SEPARATOR;
}
this.root = group;

this.expirePeriod = url.getParameter(Constants.SESSION_TIMEOUT_KEY, Constants.DEFAULT_SESSION_TIMEOUT);
this.expireFuture = expireExecutor.scheduleWithFixedDelay(new Runnable() {
public void run() {
try {
deferExpired(); // Extend the expiration time
} catch (Throwable t) { // Defensive fault tolerance
logger.error("Unexpected exception occur at defer expire time, cause: " + t.getMessage(), t);
}
}
}, expirePeriod / 2, expirePeriod / 2, TimeUnit.MILLISECONDS);
}

private void deferExpired() {
for (Map.Entry<String, JedisPool> entry : jedisPools.entrySet()) {
JedisPool jedisPool = entry.getValue();
try {
Jedis jedis = jedisPool.getResource();
try {
for (URL url : new HashSet<URL>(getRegistered())) {
if (url.getParameter(Constants.DYNAMIC_KEY, true)) {
String key = toCategoryPath(url);
if (jedis.hset(key, url.toFullString(), String.valueOf(System.currentTimeMillis() + expirePeriod)) == 1) {
jedis.publish(key, Constants.REGISTER);
}
}
}
if (admin) {
clean(jedis);
}
if (!replicate) {
break;// If the server side has synchronized data, just write a single machine
}
} finally {
jedis.close();
}
} catch (Throwable t) {
logger.warn("Failed to write provider heartbeat to redis registry. registry: " + entry.getKey() + ", cause: " + t.getMessage(), t);
}
}
}

// The monitoring center is responsible for deleting outdated dirty data
private void clean(Jedis jedis) {
Set<String> keys = jedis.keys(root + Constants.ANY_VALUE);
if (keys != null && !keys.isEmpty()) {
for (String key : keys) {
Map<String, String> values = jedis.hgetAll(key);
if (values != null && values.size() > 0) {
boolean delete = false;
long now = System.currentTimeMillis();
for (Map.Entry<String, String> entry : values.entrySet()) {
URL url = URL.valueOf(entry.getKey());
if (url.getParameter(Constants.DYNAMIC_KEY, true)) {
long expire = Long.parseLong(entry.getValue());
if (expire < now) {
jedis.hdel(key, entry.getKey());
delete = true;
if (logger.isWarnEnabled()) {
logger.warn("Delete expired key: " + key + " -> value: " + entry.getKey() + ", expire: " + new Date(expire) + ", now: " + new Date(now));
}
}
}
}
if (delete) {
jedis.publish(key, Constants.UNREGISTER);
}
}
}
}
}

public boolean isAvailable() {
for (JedisPool jedisPool : jedisPools.values()) {
try {
Jedis jedis = jedisPool.getResource();
try {
if (jedis.isConnected()) {
return true; // At least one single machine is available.
}
} finally {
jedis.close();
}
} catch (Throwable t) {
}
}
return false;
}

@Override
public void destroy() {
super.destroy();
try {
expireFuture.cancel(true);
} catch (Throwable t) {
logger.warn(t.getMessage(), t);
}
try {
for (Notifier notifier : notifiers.values()) {
notifier.shutdown();
}
} catch (Throwable t) {
logger.warn(t.getMessage(), t);
}
for (Map.Entry<String, JedisPool> entry : jedisPools.entrySet()) {
JedisPool jedisPool = entry.getValue();
try {
jedisPool.destroy();
} catch (Throwable t) {
logger.warn("Failed to destroy the redis registry client. registry: " + entry.getKey() + ", cause: " + t.getMessage(), t);
}
}
}

//注册地址到redis中主 Key 为服务名和类型
//Map 中的 Key 为 URL 地址,Map 中的 Value 为过期时间，用于判断脏数据，脏数据由监控中心删除
@Override
public void doRegister(URL url) {
String key = toCategoryPath(url);
String value = url.toFullString();
String expire = String.valueOf(System.currentTimeMillis() + expirePeriod);
boolean success = false;
RpcException exception = null;
for (Map.Entry<String, JedisPool> entry : jedisPools.entrySet()) {
JedisPool jedisPool = entry.getValue();
try {
Jedis jedis = jedisPool.getResource();
try {
jedis.hset(key, value, expire);
jedis.publish(key, Constants.REGISTER);
success = true;
if (!replicate) {
break; // If the server side has synchronized data, just write a single machine
}
} finally {
jedis.close();
}
} catch (Throwable t) {
exception = new RpcException("Failed to register service to redis registry. registry: " + entry.getKey() + ", service: " + url + ", cause: " + t.getMessage(), t);
}
}
if (exception != null) {
if (success) {
logger.warn(exception.getMessage(), exception);
} else {
throw exception;
}
}
}

//取消注册，删除key值并发送通知
@Override
public void doUnregister(URL url) {
String key = toCategoryPath(url);
String value = url.toFullString();
RpcException exception = null;
boolean success = false;
for (Map.Entry<String, JedisPool> entry : jedisPools.entrySet()) {
JedisPool jedisPool = entry.getValue();
try {
Jedis jedis = jedisPool.getResource();
try {
jedis.hdel(key, value);
jedis.publish(key, Constants.UNREGISTER);
success = true;
if (!replicate) {
break; // If the server side has synchronized data, just write a single machine
}
} finally {
jedis.close();
}
} catch (Throwable t) {
exception = new RpcException("Failed to unregister service to redis registry. registry: " + entry.getKey() + ", service: " + url + ", cause: " + t.getMessage(), t);
}
}
if (exception != null) {
if (success) {
logger.warn(exception.getMessage(), exception);
} else {
throw exception;
}
}
}

//订阅
@Override
public void doSubscribe(final URL url, final NotifyListener listener) {
String service = toServicePath(url);
Notifier notifier = notifiers.get(service);
if (notifier == null) {
//开启线程来订阅通知数据
Notifier newNotifier = new Notifier(service);
notifiers.putIfAbsent(service, newNotifier);
notifier = notifiers.get(service);
if (notifier == newNotifier) {
notifier.start();
}
}
boolean success = false;
RpcException exception = null;
for (Map.Entry<String, JedisPool> entry : jedisPools.entrySet()) {
JedisPool jedisPool = entry.getValue();
try {
Jedis jedis = jedisPool.getResource();
try {
if (service.endsWith(Constants.ANY_VALUE)) {
admin = true;
Set<String> keys = jedis.keys(service);
if (keys != null && !keys.isEmpty()) {
Map<String, Set<String>> serviceKeys = new HashMap<String, Set<String>>();
for (String key : keys) {
String serviceKey = toServicePath(key);
Set<String> sk = serviceKeys.get(serviceKey);
if (sk == null) {
sk = new HashSet<String>();
serviceKeys.put(serviceKey, sk);
}
sk.add(key);
}
for (Set<String> sk : serviceKeys.values()) {
doNotify(jedis, sk, url, Arrays.asList(listener));
}
}
} else {
doNotify(jedis, jedis.keys(service + Constants.PATH_SEPARATOR + Constants.ANY_VALUE), url, Arrays.asList(listener));
}
success = true;
break; // Just read one server's data
} finally {
jedis.close();
}
} catch (Throwable t) { // Try the next server
exception = new RpcException("Failed to subscribe service from redis registry. registry: " + entry.getKey() + ", service: " + url + ", cause: " + t.getMessage(), t);
}
}
if (exception != null) {
if (success) {
logger.warn(exception.getMessage(), exception);
} else {
throw exception;
}
}
}

@Override
public void doUnsubscribe(URL url, NotifyListener listener) {
}

private void doNotify(Jedis jedis, String key) {
for (Map.Entry<URL, Set<NotifyListener>> entry : new HashMap<URL, Set<NotifyListener>>(getSubscribed()).entrySet()) {
doNotify(jedis, Arrays.asList(key), entry.getKey(), new HashSet<NotifyListener>(entry.getValue()));
}
}

private void doNotify(Jedis jedis, Collection<String> keys, URL url, Collection<NotifyListener> listeners) {
if (keys == null || keys.isEmpty()
|| listeners == null || listeners.isEmpty()) {
return;
}
long now = System.currentTimeMillis();
List<URL> result = new ArrayList<URL>();
List<String> categories = Arrays.asList(url.getParameter(Constants.CATEGORY_KEY, new String[0]));
String consumerService = url.getServiceInterface();
for (String key : keys) {
if (!Constants.ANY_VALUE.equals(consumerService)) {
String prvoiderService = toServiceName(key);
if (!prvoiderService.equals(consumerService)) {
continue;
}
}
String category = toCategoryName(key);
if (!categories.contains(Constants.ANY_VALUE) && !categories.contains(category)) {
continue;
}
List<URL> urls = new ArrayList<URL>();
Map<String, String> values = jedis.hgetAll(key);
if (values != null && values.size() > 0) {
for (Map.Entry<String, String> entry : values.entrySet()) {
URL u = URL.valueOf(entry.getKey());
if (!u.getParameter(Constants.DYNAMIC_KEY, true)
|| Long.parseLong(entry.getValue()) >= now) {
if (UrlUtils.isMatch(url, u)) {
urls.add(u);
}
}
}
}
if (urls.isEmpty()) {
urls.add(url.setProtocol(Constants.EMPTY_PROTOCOL)
.setAddress(Constants.ANYHOST_VALUE)
.setPath(toServiceName(key))
.addParameter(Constants.CATEGORY_KEY, category));
}
result.addAll(urls);
if (logger.isInfoEnabled()) {
logger.info("redis notify: " + key + " = " + urls);
}
}
if (result == null || result.isEmpty()) {
return;
}
for (NotifyListener listener : listeners) {
notify(url, listener, result);
}
}

private String toServiceName(String categoryPath) {
String servicePath = toServicePath(categoryPath);
return servicePath.startsWith(root) ? servicePath.substring(root.length()) : servicePath;
}

private String toCategoryName(String categoryPath) {
int i = categoryPath.lastIndexOf(Constants.PATH_SEPARATOR);
return i > 0 ? categoryPath.substring(i + 1) : categoryPath;
}

private String toServicePath(String categoryPath) {
int i;
if (categoryPath.startsWith(root)) {
i = categoryPath.indexOf(Constants.PATH_SEPARATOR, root.length());
} else {
i = categoryPath.indexOf(Constants.PATH_SEPARATOR);
}
return i > 0 ? categoryPath.substring(0, i) : categoryPath;
}

private String toServicePath(URL url) {
return root + url.getServiceInterface();
}

private String toCategoryPath(URL url) {
return toServicePath(url) + Constants.PATH_SEPARATOR + url.getParameter(Constants.CATEGORY_KEY, Constants.DEFAULT_CATEGORY);
}

//创建消息订阅线程，当服务未多个的时候创建的线程也是多个，比较消耗资源
private class NotifySub extends JedisPubSub {

private final JedisPool jedisPool;

public NotifySub(JedisPool jedisPool) {
this.jedisPool = jedisPool;
}

//调用回调函数
@Override
public void onMessage(String key, String msg) {
if (logger.isInfoEnabled()) {
logger.info("redis event: " + key + " = " + msg);
}
if (msg.equals(Constants.REGISTER)
|| msg.equals(Constants.UNREGISTER)) {
try {
Jedis jedis = jedisPool.getResource();
try {
//更新本地内存中的通知数据
doNotify(jedis, key);
} finally {
jedis.close();
}
} catch (Throwable t) { // TODO Notification failure does not restore mechanism guarantee
logger.error(t.getMessage(), t);
}
}
}

@Override
public void onPMessage(String pattern, String key, String msg) {
onMessage(key, msg);
}

@Override
public void onSubscribe(String key, int num) {
}

@Override
public void onPSubscribe(String pattern, int num) {
}

@Override
public void onUnsubscribe(String key, int num) {
}

@Override
public void onPUnsubscribe(String pattern, int num) {
}

}
//接收通知线程
private class Notifier extends Thread {

private final String service;
private final AtomicInteger connectSkip = new AtomicInteger();
private final AtomicInteger connectSkiped = new AtomicInteger();
private final Random random = new Random();
private volatile Jedis jedis;
private volatile boolean first = true;
private volatile boolean running = true;
private volatile int connectRandom;

public Notifier(String service) {
super.setDaemon(true);
super.setName("DubboRedisSubscribe");
this.service = service;
}

private void resetSkip() {
connectSkip.set(0);
connectSkiped.set(0);
connectRandom = 0;
}

private boolean isSkip() {
int skip = connectSkip.get(); // Growth of skipping times
if (skip >= 10) { // If the number of skipping times increases by more than 10, take the random number
if (connectRandom == 0) {
connectRandom = random.nextInt(10);
}
skip = 10 + connectRandom;
}
if (connectSkiped.getAndIncrement() < skip) { // Check the number of skipping times
return true;
}
connectSkip.incrementAndGet();
connectSkiped.set(0);
connectRandom = 0;
return false;
}
//开启线程监听通知数据
@Override
public void run() {
while (running) {
try {
if (!isSkip()) {
try {
for (Map.Entry<String, JedisPool> entry : jedisPools.entrySet()) {
JedisPool jedisPool = entry.getValue();
try {
jedis = jedisPool.getResource();
try {
if (service.endsWith(Constants.ANY_VALUE)) {
if (!first) {
first = false;
Set<String> keys = jedis.keys(service);
if (keys != null && !keys.isEmpty()) {
for (String s : keys) {
doNotify(jedis, s);
}
}
resetSkip();
}
jedis.psubscribe(new NotifySub(jedisPool), service); // blocking
} else {
if (!first) {
first = false;
doNotify(jedis, service);
resetSkip();
}
jedis.psubscribe(new NotifySub(jedisPool), service + Constants.PATH_SEPARATOR + Constants.ANY_VALUE); // blocking
}
break;
} finally {
jedis.close();
}
} catch (Throwable t) { // Retry another server
logger.warn("Failed to subscribe service from redis registry. registry: " + entry.getKey() + ", cause: " + t.getMessage(), t);
// If you only have a single redis, you need to take a rest to avoid overtaking a lot of CPU resources
sleep(reconnectPeriod);
}
}
} catch (Throwable t) {
logger.error(t.getMessage(), t);
sleep(reconnectPeriod);
}
}
} catch (Throwable t) {
logger.error(t.getMessage(), t);
}
}
}

public void shutdown() {
try {
running = false;
jedis.disconnect();
} catch (Throwable t) {
logger.warn(t.getMessage(), t);
}
}

}

}